Loading...
Are the CTV-to-PTV margins currently used in online adaptive radiotherapy for prostate cancer too large? The impact of the distribution of microscopic disease on treatment margin requirements
Dassen, M. G. van Herk, M. Witte, M. G. Janssen, T. Pos, F. van der Heide, U. A.
Dassen, M. G.
van Herk, M.
Witte, M. G.
Janssen, T.
Pos, F.
van der Heide, U. A.
Abstract
Purpose Planning target volume (PTV) margin recipes assume all parts of the target are equally important. For the prostate clinical target volume (CTV) this is invalid. We evaluated the impact of the spatial probability distribution of microscopic disease in the prostate on CTV-to-PTV margins. Materials and methods A prostate with a volume of 44 cm(3) was defined as CTVprostate. Homogenous dose distributions were created with margins ranging 0-5 mm. The gross tumor volume (GTV) was assumed covered with a separate margin. Microscopic satellites were sampled within the CTVprostate from a histopathology-based probability distribution for a range of numbers (1-10) and sizes (0.02-0.2 cm(3)) to define CTVsatellites. Geometric errors were sampled from a 3D Gaussian distribution, simulating online adaptive treatment of 5 fractions. Each CTV was shifted with respect to the dose according to each total error. The PTV margin ensuring 95 % of the prescribed dose to the CTVsatellites in 90 % of simulations was determined and compared with CTVprostate. Results For systematic errors with width (Sigma) 0.5 mm and random errors with width (sigma(r)) 1.5 mm, the margin for the CTVprostate was 3 mm, whereas for each definition of CTVsatellites this margin was 0-1 mm. For sigma(r) = 2.7 mm, a margin of 5 mm was adequate for the CTVprostate and 2-3 mm for all except the most favourable and unfavourable CTVsatellites definition. Conclusion The CTV-to-PTV margins used in online adaptive radiotherapy for prostate cancer can be reduced by similar to 2 mm, if the GTV is covered with an adequate margin.
Description
Date
2026
Publisher
Collections
Files
Loading...
Found from Unpaywall
Adobe PDF, 2.32 MB
Keywords
Type
Article
Citation
Dassen MG, van Herk M, Witte MG, Janssen T, Pos F, van der Heide UA. Are the CTV-to-PTV margins currently used in online adaptive radiotherapy for prostate cancer too large? The impact of the distribution of microscopic disease on treatment margin requirements. Radiotherapy and Oncology. 2026 MAR;216.